Installations for extracting and breaking up minerals, and in particular crushing and grinding material, are subjected to numerous constraints of performance and costs.
As an example, one might cite in the area of the treatment of aggregates, of cement and of minerals, wear parts such as ejectors and anvils of grinding machines with vertical shafts, hammers and breakers of grinding machines with horizontal shafts, cones for crushers, tables and rollers for vertical crushers, armoured plating and elevators for ball mills or rod mills. With regard to mining extraction installations, one might mention, among others, pumps for bituminous sands or drilling machines, pumps for mines and dredging teeth.
The suppliers of wear parts for these machines are faced with increased demands for wear parts which meet the constraints of resistance to impact and resistance to abrasion at the same time.
Traditional materials generally meet one or the other of these types of requirement but are very rarely resistant to both impact and abrasion. Indeed, ductile materials offer enhanced resistance to impact but have very little resistance to abrasion. On the other hand, hard abrasion-resistant materials have very little resistance to violent impact.
Historically, the first reflections on this problem led to an exclusively metallurgical approach which consisted in suggesting steels with manganese that are very resistant to impacts and nevertheless achieve intermediate hardness levels of the order of 650 to 700 Hv (Vickers hardness).
Other alternatives such as castings with chrome have also been suggested. These allow to achieve hardness levels of the order of 700 to 850 Hv after suitable thermal treatment. These values are achieved for alloys containing a percentage of carbide up to 35%.
Currently, bimetallic castings have also been used, but these nevertheless have the disadvantage of being limited to parts of simple shape, which drastically reduces their opportunities for industrial application.
Wear parts are generally considered as consumables, which means that apart from purely technical constraints, there is also a financial constraint which limits the opportunities for solutions that have an average cost of US$4/Kg. It is generally estimated that this price level, which is twice as high as that of traditional wear parts, is the threshold of financial acceptability for customers.